Method of protecting tin-packings against corrosion and making them glossy

ABSTRACT

TIN-PACKING, I.E. TIN-CANS FOR FOOD ARE PROTECTED AGAINST CORROSION AND MADE GLOSSY AT THE SAME TIME BY A METHOD IN WHICH A TIN-PACKING IS TREATED WITH A MIXTURE OF INORGANIC AND ORGANIC CORROSION INHIBITORS HAVING A COMMON ANION AND HAVING A SYNERGISTIC EFFECT TOGETHER WITH WASHING AND BRIGHTENING AGENTS.

United States Patent (Ofice 3,822,998 METHOD OF PROTECTING TIN-PACKINGS AGAINST CORROSION AND MAKING THEM GLOSSY Romuald Juchniewicz, Gdansk, Poland, assignor to Politechnika Gdanska Majakowskiego, Gdansk, Poland No Drawing. Continuation of abandoned application Ser. No. 872,748, Oct. 30, 1969. This application June 30, 1972, Ser. No. 267,983 Claims priority, application Poland, Oct. 10, 1968,

- 129,973/ 68 Int. Cl. C23f 11/02, 11/16, 11/18 US. Cl. 21-2.7 A 8 Claims ABSTRACT OF THE DISCLOSURE Tin-packings, i.e. tin-cans for food are protected against corrosion and made glossy at the same time by a method in which a tin-packing is treated with a mixture of inorganic and organic corrosion inhibitors having a common anion and having a synergistic effect together with washing and brightening agents.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of Ser. No. 872,748 filed Oct. 30, 1969, and now abandoned.

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to protecting tin packings against corrosion and rendering them glossy.

Prior Art The known method of protecting tin packings against corrosion consists mainly in coating the packings, after sterilization or pasteurization thereof, with temporary protective agents in the form of an emulsion, a grease layer or a paraffin layer.

A disadvantage of these methods is the fact that they provide insufficient protection against corrosion since, in spite of the presence of the layer of inhibiting agent, the corrosion process which is initiated during sterilization or pasteurization continues while the tin-packing is stored.

In the literature Applicant has found no method for protecting against corrosion and imparting a gloss to tinplate packings which involve the introduction of a mixture of inhibitors into the water used during the sterilization and pasteurization processes. On the other hand, there are a number of patents disclosing the use of inorganic and organic inhibitor mixtures with various additives causing a synergistic effect for many industrial appilcations. These mixtures, mainly empirically arrived at, are not based on the theoretical considerations involved in the present invention.

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is the provision of a method of protecting tin-packings, particularly for tinned foods, against corrosion and for making them glossy.

The method according to the present invention is based on the fact that a mixture of inorganic and organic corrosion inhibitors having a common anion produces a synergistic effect in preventing corrosion and with the cooperation of washing and brightening agents, the mixture causes a strong anodic polarization in the steel-tin coating cell. The mixture of inhibitors forms a stable complex which, by being adsorbed on the surface of the metal, decreases the binding force of the metal with the passivating oxygen, maintains the potential of the packing below the critical value at which pit formation occurs and deepens the passivating properties of the solution. The processes 3,822,998 Patented July 9, 1974 chemical compounds of a strictly determined qualitative A and quantitative composition in which the process of protecting against corrosion and that of imparting a gloss to the packing proceed jointly with the sterilization or pasteurization process.

According to the chemical composition of the water and its hardness, as well as to the kind of sheet metal used for the packings, an inhibitor mixture, consisting of an inorganic inhibitor, an organic inhibitor having a common anion, a washing agent and a brightener, is dissolved in water and added with continuous stirring to water contained in a pasteurization tank or autoclave which is filled with packings for sterilization. In steam autoclaves, the mixture is placed in the form of a paste in a perforated container in the autoclave at the steam inlet. In horizontal autoclave, the bottom of the autoclave may be strewn with the mixture or the mixture may be placed in a perforated container near the steam or Water inlet.

Among the inorganic inhibitors there are included disodium phosphate, sodium hexametaphosphate, water glass, sodium nitrite, and borax. Among the organic inhibitors having a common anion and which together with the other additives produce a synergistic effect, there are, for example, the phosphates: triethanolamine phosphate, hexamethylenetetramine phosphate, p-nonylphenol phosphate, styrophene phosphite; the silicates: 4-phenoxysilanc, 4 butoxysilane, calcium, silanolate, aminoalkylpolysiloxane; the nitrites: guanidine nitrite, diisobutylamine nitrite, piperidine nitrite, dicyclohexylamine nitrite; the borates: hydrated cyclohexylamine borate, triethanolamine borate, boric acid triphenyl ester. As the washing agents, there are used water glass, sodium dodecylbenzenesulphonate, ethoxylized anhydrosorbite oleate, ethoxylized pentaerythrite monooleate, ethoxylized p-nonylphenol; and as the brightener there is used sodium perborate.

The amount of the inhibitor mixture is determined in relation to the amount of water used for pasteurization or sterilization of the tin-packings. It is also dependent on the chemical composition and hardness of the water, as well as on the kind of sheet metal used. The amount is usually 0.05 %0.6% by weight; the percent share of the individual components of the mixture is as follows:

Percent Inorganic inhibitors 40-60 Organic inhibitors having a common anion 15-45 Washing agents 10-20 Brightener 5-20 The solutions based on phosphate inhibitors have a pH of about 9, nitrite solutions always are above pH 6.5, silicate solutions are up to pH 7, and borate solutions about pH 7. The modulus of the water glass used should be about 2-4.

After the pasteurization or sterilization process, the dried or wiped packing is passed, without any necessity of using an additional preservative, to storage, where the packings are isolated from one another by means of plates which are saturated with a mixture of inhibitors of which one may be a volatile corrosion inhibitor.

The method according to the present invention is more fully explained in the following Examples.

Example I To 1000 liters of technological water of of German hardness, which are used for the sterilization of 1000 0.5 kg. cans made of electrolytic tin-plate, there are added with constant stirring, a solution consisting of the following previously dissolved in water:

250 g. of disodium phosphate 100 g. of triethanolamine phosphate 100 g. of sodium dodecylbenzenesulphonate 100 g. of sodium perborate 250 g. of water glass.

The above is a homogeneous inhibitor solution having a pH value of about 9, and the sterilization is carried out therein. The cans, after being dried or wiped free of the superficial water layer, are directed, without any additional preservation, to storage where they are separated from one another by means of plates saturated on both sides with sorbate monooleate. The thus secured packings do not corrode at all during a two year period of storage.

Example II To 500 liters of technological water of 2 of German hardness used for the pasteurization of 500 1 kg. packings made of hot tin-plate, the following is added with continuous stirring, after being previously dissolved in water:

200 g. of sodium nitrite 90 g. of diisobutylamine nitrite 75 g. of ethoxylized pentaerythrite monooleate 75 g. of sodium perborate 250 g. of water glass.

The above is a homogeneous inhibitor solution having a pH value of about 8.5 and pasteurization is carried out therein. The dried packings are separated from each other by means of plates saturated on both sides with ethoxylized pentaerythrite monooleate. Thus secured packings do not corrode within up to two years of storage.

Example III In a steam pressure autoclave, at the steam inlet, there is suspended a perforated container containing an inhibitor mixture of paste consistency and composed of:

250 g. of water glass 250 g. of sorbate monooleate 150 g. of sodium perborate 250 g. of disodium phosphate 50 g. of hexamethylenetetramine phosphate.

Example IV To 500 liters of technological water of 10 of German hardness, used for the pasteurization of 500 1 kg. packings made of electrolytic tin-plate there are added with continuous stirring, previously dissolved in water:

250 ml. of water glass of a modulus of 2-4 100 g. of 4-butoxysilane 70 g. of ethoxylized anhydrosorbite oleate 70 g. of sodium perborate.

The above is a homogeneous inhibitor solution having a pH value of about 7 and the pasteurization is carried out therein. The cans, after being dried or wiped free of superficial water are directed, without any additional preservation, to a storage area where they are separated from each other by means of plates saturated on both sides with a mixture of sorbate monooleate and pentaerythritemonooleate with an addition of dicyclohexylamine nitrite. These packings do not corrode even after two years of storage.

Example V To 500 liters of technological water of 14 of German hardness, used for the sterilization of 500 0.5 kg. packings made of hot tin-plate, there is added with continuous stirring to an autoclave, a water solution of:

200 g. of borax g. of triethanolamine borate 75 g. of ethoxylized pentaerythrite monooleate 75 g. of sodium perborate.

The above is a homogeneous inhibitor solution having a pH value of about 7.5 and sterilization in a pressure autoclave is carried out using said solution. The cans, after being dried or wiped free of the superficial water layer are directed, without any additional preservation, to storage, where they are separated from each other by means of plates saturated on both sides with parafiin oil, to which 50% of pentaerythrite monooleate has been added. Thethus treated packings do not corrode, even after two years of storing.

Example VI In a horizontal autoclave, the bottom of the autoclave is strewn with a mixture consisting of the following inhibitors:

300 g. of water glass 250 g. of disodium phosphate 100 g. of p-nonylphenol phosphate 75 g. of ethoxylized pentaerythrite monooleate 100 g. of sodium perborate be introduced during 3 sterilization operations and the fourth operation is carried out without inhibitors.

The invention finds application in various fields of the food industry producing tinned preserves. The serviceable and technical advantages resulting from the use of the present invention consist in the elimination of corrosion of packings during the production and storage, improvement of the external appearance, preventing corrosion of the autoclaves, vehicles and equipment used in the sterilization or pasteurization process. Furthermore, the packings need no grease or emulsion coating, thus creating better labeling conditions and improving the external appearance of the packings, since the labels have no fat drippings. Also, the costs of cleaning the packings are decreased.

What is claimed is:

1. A method for preventing corrosion and imparting glossiness to tin-packings during the sterilization or pasteurization thereof with water, said method comprising adding to the water used in said sterilization or pasteurization, a mixture comprising (a) at least one member of the group consisting of disodium phosphate and sodium.

hexametaphosphate; (b) an organic derivative of said at least one member having an anion in common with said at least one member; (c) a washing agent and (d) a brightening agent, the organic derivative being at least one member selected from the group consisting of triethanolamine phosphate, hexam'ethylenetetramine phosphate,

and p-nonylphenol phosphate.

2. A method according to claim 1, wherein the washing agent is at least one member selected from the group consisting of water glass, sodium dodecylbenzene sulphonate,

ethoxylized anhydrosorbite oleate, ethoxylized pentaerythrite monooleate and ethoxylized p-nonylphenol.

3. A method according to claim 1, wherein the brightening agent is sodium perborate.

4. A method according to claim 1, wherein the mixture is used in an amount of ODS-0.6% based on the weight of Water usedin the sterilization or pasteurization and the mixture is constituted by 40-60% of said at least one member, 15-45% of said organic derivative, -20% of said washing agent and 520% of the brightening agent.

5. A method according to claim 1, wherein the sterilization or pasteurization is effected in a steam autoclave and the mixture is placed in a perforated container near the steam inlet.

6. A method according to claim 1, wherein the sterilization or pasteurization is effected in a horizontal water autoclave and the mixture is placed in a perforated container near the water inlet.

7. A method according to claim 1, wherein after the sterilization or pasteurization, the tin-packings are dried and separated from one another by plates saturated with corrosion inhibitors.

8. A method according to claim 2, wherein said corrosion inhibitors saturating the plates include at least one volatile inhibitor.

References Cited UNITED STATES PATENTS 2,643,177 6/ 1953 Wachter et al.

2,675,351 4/1954 Ulmer et al 21-27 R 2,815,328 12/1957 Green et al. 252-389 R X 2,817,636 12/1957 Barker 252-389 R X 2,901,438 8/1959 Rogers 252389 A X 2,943,909 7/ 1960 Wachter et a1 21--2.7 R 3,046,230 7/1962 Berger 252-389 R X 3,234,144 2/1966 Morehouse 252389 R 3,240,707 3/1966 Dulat 252389 R X 3,445,179 5/1969 Jansen 212.7 R 3,510,436 5/ 1970 Silverste-in et al. 212.7 R X BARRY S. RICHMAN, Primary Examiner US. Cl. X.R.

21-2, 2.5 A, 2.5 B, 2.7 R, 57; 134-2, R; 252389 A Patent No. D d 9,

Romuald Juchniewicz Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 10 and 11, "Oct. 10'," I968, 129,973/68" should read Oct; 30, 1968 Signed and sealed this 4th day of'Februar'y 1975.

(SEAL) Attest:

McCOY GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 998 Dated July 9 1974 v Romuald Juchniewicz Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, lines 10 and 11, "Oct. 10'," I968, 129,973/68" should read Oct; 30, 1968 Signed a nd sealed this 4th day ofFebru'ary 1975.

(SEAL) Attest: I

McCOY M. GIBSONJR. c. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 s zevriwzm PRINTING crrlcs 930 

